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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Wait-free Hazard Pointers Using Std Atomics
Date: Thu, 26 Jun 2025 22:26:53 -0700
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In-Reply-To: <103bc9h$175qq$1@dont-email.me>

On 6/23/2025 4:03 AM, jseigh wrote:
> On 6/3/25 15:09, Chris M. Thomasson wrote:
>> On 6/2/2025 3:07 PM, jseigh wrote:
>>> On 6/1/25 16:31, Chris M. Thomasson wrote:
>>>> On 5/29/2025 2:17 PM, jseigh wrote:>>>
>>>>>
>>>>> Push may wait-free but pop isn't event lock-free.
>>>>
>>>
>>>>
>>>> Actually, I like my futex stack experiment as is. normal CAS for 
>>>> push, SWAP for pop. It needs to have multiple stacks and distribute 
>>>> across them because popping all from a single stack can mean a 
>>>> thread gets too much work. Push lock-free, pop wait-free.
>>>>
>>>>
>>> Well you actually have a lot of leeway in concurrent queue semantics.
>>> Drop the FIFO requirements since they're not really observable for
>>> all practical purposes and just concentrate on throughput forward
>>> progress.
>>>
>>> And wait-free is highly overrated. It seems to be important only in
>>> theses, technical papers and obscure blogs, not so much is real world
>>> applications which is one reason I not going to implement it.
>>
>> Perhaps. However, using a loop-free exchange is "faster" than a loop 
>> based CAS? On Intel, XCHG vs a CMPXCHG loop?
>>
>>
>>>>
>>>>>
>>>>> Anyway, after some consideration, I'm off on this
>>>>> wait-free hazard pointer.  The lock-free version is
>>>>> more than performant.
>>>
>>> I did post on my blog how to improve reclaim forward progress for the
>>> wait-free hazard pointer so it's equivalent to a proxy collector.
>>
> 
> I've been doing reader lock-free too long.  I just realized how
> trivially simple it is to do read write lock-free for almost any data
> structure.  That's slightly embarrassing.

:^) Indeed. But, its not a bad skill to have. Well, at least to me.